fix(installer): wait for prior service registration to clear before create

After `sc delete`, the service stays in "marked for deletion" state until
every open handle (services.msc, Task Manager Services tab, Event Viewer,
prior sc query process) is closed. The installer used to immediately call
`sc create` and hit a silent hang / confusing "specified service has been
marked for deletion" error.

Poll `sc query` for up to 30s after delete; if the service is still
registered past that, fail with actionable guidance (close the offending
console or reboot). Also translate exit 1072 from `sc create` into the
same human-readable hint.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/ClaudeDo.Installer/Steps/RegisterServiceStep.cs

@@ -23,6 +23,24 @@ public sealed class RegisterServiceStep : IInstallStep
         progress.Report("Removing existing service registration (if any)...");
         await RunSc($"delete {ServiceName}", ctx, progress, ct, ignoreErrors: true);
 
+        // Wait for the service to actually disappear from SCM. `sc delete` returns
+        // immediately but the service stays "marked for deletion" until every open
+        // handle (services.msc, Task Manager, a prior sc query process) is closed.
+        // Poll up to 30s — then fail with actionable guidance if it's still there.
+        progress.Report("Waiting for prior service registration to clear...");
+        for (var i = 0; i < 30; i++)
+        {
+            ct.ThrowIfCancellationRequested();
+            var (queryExit, _) = await RunSc($"query {ServiceName}", ctx, progress, ct, ignoreErrors: true);
+            if (queryExit != 0) break; // service no longer registered — good
+            if (i == 29)
+                return StepResult.Fail(
+                    $"Service '{ServiceName}' is marked for deletion but hasn't cleared after 30s. " +
+                    "Close any open Services console (services.msc), Task Manager Services tab, or " +
+                    "Event Viewer showing the service, then retry. A reboot will also clear it.");
+            await Task.Delay(1000, ct);
+        }
+
         // Create service
         var startType = ctx.AutoStart ? "auto" : "demand";
         var createArgs = $"create {ServiceName} binPath= \"{workerExe}\" start= {startType}";
@@ -35,6 +53,10 @@ public sealed class RegisterServiceStep : IInstallStep
 
         progress.Report("Creating service...");
         var (exitCode, output) = await RunSc(createArgs, ctx, progress, ct);
+        if (exitCode == 1072)
+            return StepResult.Fail(
+                $"Service '{ServiceName}' is still marked for deletion. " +
+                "Close services.msc / Task Manager / Event Viewer and retry, or reboot.");
         if (exitCode != 0)
             return StepResult.Fail($"sc.exe create failed (exit {exitCode}): {output}");